On Tuesday, the Dow component is expected to launch Office 365, which is believed to include a hosted version of its Exchange email product. S&P reiterated a buy rating on Microsoft on Monday ahead of the launch.

"We view this development as a positive, as the company competes with Google ( GOOG) in the emerging online productivity suite market," the firm wrote. "We believe revenues from its monthly subscription fees will be incremental at first, but think they will eventually cannibalize sales of Microsoft Office, as customers shift from a desktop version of the software to the cloud computing version."